This invention relates to an organic-inorganic hybrid free standing film and its production process. More specifically, this invention relates to an organic-inorganic hybrid free standing film containing an organic polymer containing a constitutional repeating unit derived from a particular monomer and a hydrolytic condensate of a metal alkoxide as its main components, and its production process.
Free standing thin films (hereinafter also referred to as free standing films) having a thickness in the order of nanometer to micrometer have recently provoked a growing attention since they are one of important materials whose commercialization is sincerely awaited in various advanced fields such as electronics, environment, and life sciences. Exemplary applications include reverse osmosis membrane used in producing fresh water from sea water, separator membrane used in separating gas and ion, and structural member of sensor and display device.
However, production of a free standing film having its thickness controlled to the degree of nanometer is quite difficult and risk of defects such as pin holes increases with the decrease in the film thickness. A free standing film with reduced thickness is also like to suffer from problems such as brittleness and insufficient strength. As a means to produce a free standing film having sufficient mechanical strength and flexibility, Vendamme, R. et al. (Vendamme, R. et al. “Robust free-standing nanomembranes of organic/inorganic interpenetrating networks”, Nature materials, 2006, vol. 5, pp. 494-501) proposes use of a hybrid film of an organic polymer and an inorganic compound, namely, the so-called organic-inorganic hybrid thin film. According to JP 10-306109 A, an “organic-inorganic hybrid material” means a novel material which is provided with the excellent heat resistance and mechanical strength of the inorganic compound as well as the excellent flexibility and chemical properties of the organic compound. In Vendamme, R. et al., a thin film having a thickness in the order of nanometer is formed by spin coating a mixture of a monomer having hydroxy group and a zirconia precursor to simultaneously promote radical polymerization of the monomer and hydrolytic condensation of the zirconia precursor.